The prior art closest to the present invention known is U.S. Pat. No. 3,832,665; Aug. 27, 1974 to A. Belcher for BLOWN FUSE INDICATOR FOR HIGH-VOLTAGE FUSES. U.S. Pat. No. 3,621,433; Nov. 16, 1971 to R. A. Belcher for ELECTRIC FUSE HAVING PLUG TERMINALS is also of interest as prior art.
The simplicity of the fuse according to this invention is in part due to the fact that all its component parts form a bench-assembly capable of being inserted as a whole by one single act into the casing, or fuse tube.
Another reason for the simplicity of this invention is also the fact that the aforementioned bench-assembly is itself of great simplicity and easily to be assembled.
Further features of this invention and advantages thereof will become more apparent as this specification proceeds.
A fuse according to this invention comprises
(a) a tubular casing of heat resistant and heat shock resistant electric insulating material such as e.g., a synthetic resin glass cloth laminate;
(b) a metal plug having a predetermined outer diameter inserted into one end of said casing and plugging said one end;
(c) said plug having a coaxial extension integral with said plug, extending beyond said casing and having a smaller outer diameter than said plug;
(d) said plug and said extension are tubular, i.e. they define a passageway in a direction longitudinally thereof;
(e) a spring-biased blown fuse indicator arranged inside said passageway is positioned at the axially outer end thereof;
(f) a plurality of parallel rods of an electric insulating material defining a prismatic space is supported on one end thereof by said plug;
(g) a perforated metal disk arranged inside said casing positioned close to the other end thereof is supporting the other end of said plurality of parallel rods;
(h) a fusible element wound in several turns substantially helically around said plurality of rods and conductively connecting said plug to said perforated disk;
(i) a restraining wire for said blown fuse indicator of which one end is conductively connected to said perforated disk and the opposite end is conductively connected to said blown fuse indicator;
(j) a cover covering the axially inner end of said passageway, said restraining wire being threaded through an aperture in said cover and an abutment on said restraining wire engaging said cover and precluding movement of said cover away from said axially inner end of said passageway;
(k) a pulverulent arc-quenching filler inside said casing filling the entire volume thereof not occupied by other parts;
(l) said plug and said extension thereof, said spring-biased blown fuse indicator, said restraining wire, said cover for said passageway, said plurality of rods of electric insulating material, said fusible element and said perforated disk, forming a sub-assembly capable of being introduced into said casing from one end thereof; and
(m) a ferrule mounted on said casing adjacent said perforated metal disk and engaging with the lateral walls thereof the lateral walls of said casing.